1. Field of the Invention
This invention relates to a semiconducting member, a functional member for electrophotography and a process cartridge. More particularly, it relates to a semiconducting member containing a water-soluble polyaniline, and a functional member for electrophotography and a process cartridge which have such a semiconducting member.
2. Related Background Art
In recent years, with progress of electrophotographic techniques, there is an increasing demand for semiconducting members used in electrophotographic processing. In particular, elastic-rollers used in processing such as charging, developing and transfer attract notice. As semiconducting members used for such purposes, required are those having less uneven electrical resistivity depending on positions, having less dependence of electrical resistivity on applied voltage, having a small width of variations in electrical resistivity when used in environments of low temperature and low humidity and up to high temperature and high humidity and also having a small width of variations in electrical resistivity when used continuously for a long time.
The semiconducting members used for such purposes are comprised of a polymeric substance such as a polymeric elastomer or a polymeric foam in which a conductive material has been mixed. This conductive material is roughly grouped into a powdery material and a soluble (water-soluble) material.
Of these conductive materials, when the powdery material, e.g., carbon black powder or metal powder is used, the state of dispersion of inorganic conductive materials in thermoplastic resins is important because the mechanism by which it exerts conductivity relies on mutual contact of conductive material particles, and there has been a tendency of causing great changes in electrical resistivity depending on any slight difference in processing conditions and difference in mixing proportions. Also, even the same molded product may have a greatly uneven electrical resistivity depending on positions. Thus, it is difficult to obtain molded products showing stable semiconducting properties, in a good reproducibility. In general, in a system where the powdery material is added, phenomenons as stated above especially tend to occur in a semiconducting region ranging from 1xc3x97104 to 1xc3x971012 xcexa9xc2x7cm, and it is difficult to control electrical resistivity. Also, mixing the powdery material in a large proportion in order to achieve a lower electrical resistivity may cause a problem that products have a low mechanical strength and a rough surface. There is another problem that such a powdery material, having once been dispersed, again agglomerates in the thermoplastic resin to cause a change in electrical resistivity. Thus, the powdery materials have had problems caused by dispersion uniformity and stability.
As for the soluble material, it may include conducting agents comprised of inorganic ionic materials as exemplified by lithium perchlorate, sodium perchlorate and calcium perchlorate, and organic ionic materials as exemplified by cationic surface-active agents such as lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, octadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride and modified fatty acid dimethylethylammonium ethosulfate, amphoteric surface-active agents such as laurylbetaine, stearylbetaine and dimethylalkyllaurylbetaine, and quaternary ammonium salts such as tetraethylammonium perchlorate, tetrabutylammonium perchlorate, tetrabutylammonium borofluoride; and polymeric members are also known which have been adjusted to have a stated resistivity, by mixing at least one of any of such conducting agents and an antistatic agent such as a hydrophilic polyether or polyester in the polymeric substance such as a polymeric elastomer or a polymeric foam. The polymeric members of this type, however, have a problem that they have a large width of variations in electrical resistivity when used in environments of low temperature and low humidity and up to high temperature and high humidity (i.e., have a poor environmental stability).
Thus, in these known conductive materials, it has been difficult to obtain semiconducting members that satisfy all of dispersion uniformity, dispersion stability and environmental stability.
The present inventors made extensive studies on conductive materials that can solve these problems. As the result, they have found that a water-soluble polyaniline is a conductive material which provides the semiconducting members that satisfy all of dispersion uniformity, dispersion stability and environmental stability.
Polyaniline as a conductive material is already known in the art. Its conductivity is imparted through protonic doping or oxidation doping. The polyaniline can be synthesized from relatively inexpensive monomers in a high yield. As to the form of its conductivity, it is well known that the polyaniline has good chemical properties and relatively high electrical conductivity and environmental stability.
However, the polyaniline has so stiff a backbone chain structure and so great a mutual action between high-molecular chains that it is commonly insoluble and infusible and has a disadvantage of being moldable or workable with difficulty.
In recent ten years or so, a large number of studies made on solubilization have brought about considerable progress, and development has been made on a polyaniline that is soluble in organic solvents and water and on methods for its working.
There is an example in which a conductive composition containing a polymeric compound including this water-soluble polyaniline is used in antistatic agents or the like. There, however, is no example in which it is used as an electrophotographic functional member required to have high-grade uniformity in conductivity and environmental stability.
An object of the present invention is to provide a semiconducting member which is readily controllable to a stated electrical resistivity, has less uneven electrical resistivity depending on positions, has a small width of variations in electrical resistivity when used in environments of low temperature and low humidity and up to high temperature and high humidity and also has a small width of variations in electrical resistivity when used continuously for a long time, and to provide a electrophotographic functional member and a process cartridge which have such a semiconducting member.
To achieve the above object, the present invention provides a semiconducting member comprising a water-soluble polyaniline having an acidic group, and an aqueous polymeric compound;
the semiconducting member having a volume resistivity of from 104 xcexa9xc2x7cm to 1012 xcexa9xc2x7cm.
The present invention also provides a functional member for electrophotography, comprising a support and a functional layer;
the functional layer comprising a semiconducting member comprising a water-soluble polyaniline having an acidic group, and an aqueous polymeric compound;
the semiconducting member having a volume resistivity of from 104 xcexa9xc2x7cm to 1012 xcexa9xc2x7cm.
The present invention also provides a process cartridge comprising an electrophotographic photosensitive member and a functional member;
the electrophotographic photosensitive member and functional member being supported as one unit and being detachably mountable to the main body of an electrophotographic apparatus;
the functional member comprising a support and a functional layer;
the functional layer comprising a semiconducting member comprising a water-soluble polyaniline having an acidic group, and an aqueous polymeric compound;
the semiconducting member having a volume resistivity of from 104 xcexa9xc2x7cm to 1012 xcexa9xc2x7cm.